High Energy Astrophysical Phenomena
KPolaris: GPU-accelerated Polarized Radiative Transfer in General Relativity
Zelin Zhang and Bin Chen
Polarized black-hole images carry information about both the magnetized
plasma and the curved spacetime through which the radiation propagates. We present KPolaris, an open-source GPU-accelerated general-relativistic polarized radiative-transfer code built on the Kokkos framework. It supports analytic
plasma models and GRMHD simulation data, with both fast-light and slow-light radiative transfer. The code also provides diagnostics that connect image structure to the emitting
plasma and to propagation effects along the rays. These include emissivity-weighted
plasma maps, emission contributions from selected regions, selected-ray histories, and sensitivities of the Stokes parameters to
plasma parameters. Numerical convergence tests and comparisons with an independent radiative-transfer code assess the accuracy of the calculations. GPU acceleration reduces the computational cost of image generation, facilitating multi-frequency and time-dependent studies of polarized black-hole images.
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Solar and Stellar Astrophysics
Are there really some eccentric eclipsing binaries having orbital periods below 1 d?
P. Zasche and M. Wolf
The stellar binary systems are classical tools for studying dynamics, and tidal circularization is one of the processes taking place in these. During the last few years, several dozen systems have been published supposedly having orbital periods shorter than 1 d, and have also been published as having eccentric orbits. Such a configuration is due to their spatial closeness, and the tides very improbable. Therefore, we performed a thorough analysis of all these eclipsing binaries (>140), showing that the vast majority of the published systems (> 98%) are in fact circular. Especially, the eclipsing binaries identified and published from the Gaia DR3 catalogue suffer from a lack of data, and about 50 per cent had incorrectly derived periods. This mostly incorrect identification of the eccentric orbits is due to automatic pipelines and routines running without human checking/validating, and also due to the large number of systems with (evolving) spots on the surfaces of either of the
stars. Only two eccentric orbits were found below the 1-d period limit, while the
star TIC 1190662 with an orbital period of about 0.888 d has a surprisingly large value of eccentricity about 0.21.
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High Energy Astrophysical Phenomena
Einstein Probe discovery of the magnetar EP J223759.5+531421
N. Rea, F. Coti Zelati, A. Borghese et al. (+44 more)
We report the discovery and early outburst
evolution of the new Galactic magnetar EP J223759.5+531421, detected by the Einstein Probe Wide-field X-ray
Telescope on 2026 June 28. Follow-up observations with Einstein Probe, XMM–Newton, NuSTAR, SVOM, and IXPE revealed coherent X-ray pulsations at P ~ 6s and an average period derivative of Pdot ~ 2.8x10^{-12} s/s. These values imply a nominal polar dipolar
magnetic field of B_dip ~ 2.6x10^{14} Gauss and a characteristic age of tau_c ~ 34 kyr, although the structured timing residuals suggest possible torque variability. The rms pulsed fraction is approximately 20-25% below ~7 keV and decreases at higher energies. The broadband spectra require multiple thermal components and a hard power-law tail. Adopting a distance of 3.3 kpc, the 0.5-30 keV luminosity declined from 1.2x10^{35} to 5.7x10^{34} erg/s during the first month, accompanied by a decrease in the inferred thermal-emitting areas. At this distance, the Galactic latitude b=-4.56 deg corresponds to a height of approximately 0.26 kpc below the Galactic plane, which is difficult to reconcile with the nominal characteristic age under a simple midplane-birth scenario even for an extreme proper motion velocity. Short X-ray bursts independently confirm the magnetar nature of the source. No near-infrared or
radio counterpart were detected by GTC, Medicina or FAST, respectively, down to K_s>21 mag and S_{1.25 GHz} <2.3 microJy. These observations demonstrate the potential of the Einstein Probe WXT monitoring to uncover previously quiescent Galactic magnetars and follow their outbursts from their earliest observed stages.
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All authors N. Rea, F. Coti Zelati, A. Borghese, Y.L. Wang, H. Yang, X. Mao, C.-Y. Dai, E. Arrigoni, J. Bai, G. Bernardi, M. Burgay, S. Cao, A. Coleiro, D. De Grandis, P. Esposito, H. Feng, Y.-C. Fu, A. Geminardi, D. Götz, S. Guillot, Y. Huang, M. Imbrogno, G. L. Israel, C. Jin, A. Kong, Y. Li, L. Lin, C.-S. Liu, C. Maitra, A. Marino, S. Mereghetti, J.-U. Ness, S. Ng, M. Pilia, A. Possenti, H. Sun, L. Tao, R. Taverna, A. Tiengo, R. Turolla, W. Yuan, S. Zane, B. Zhang, L.-X. Zhang, Z. Zhang, W.-W. Zhu, Y.-C. Zou
Instrumentation and Methods for Astrophysics
Options for Compression of radio interferometry data: lossy compression of visibilities and lossless compression of uv-visibility grids for the MHONGOOSE survey
Richard Dodson, Jonghwan Rhee, W.J.G. de Blok et al. (+6 more)
Next generation
radio astronomy
telescopes are challenging existing data reduction paradigms. With ever more
antennas, larger bandwidths, and sometimes multiple primary beams, they often generate more observed data products than can readily be stored long-term. Thus, data storage becomes a major cost driver and processing constraint. In this paper, we test two methods of addressing this problem: grid-stacking, a two-stage lossless compression solution; and the lossy compression of the raw visibilities before traditional processing. To demonstrate these solutions we utilised a deep imaging pipeline based on software for the ASKAP
telescope, ASKAPSoft, but applied to a strong source (NGC1566) from the deep MeerKAT HI spectral line project, MHONGOOSE. The grid-stacking solution reproduces the spectrum from traditional processing to within better than 0.7%, and also allows for the reconstruction of other weighting scales without significant computing costs. In comparison, image-stacking also reproduces the spectrum from the traditional processing, to within better than 3% but with worse image residuals in the cube. The lossy compression, even at a near ten-fold reduction in file size, reproduces the spectra almost perfectly (to better than ~0.01% in all cases). Thus both compression methods are promising solutions, and we discuss considerations for their application.
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All authors Richard Dodson, Jonghwan Rhee, W.J.G. de Blok, Martin Meyer, Alexander Williamson, Daniel Mitchell, Kristóf Rozgonyi, María J. Rioja, Pascal J. Elahi
High Energy Astrophysical Phenomena
IXPE observation of the new magnetar source EP J223759.5+531421
Roberto Taverna, Lorenzo Marra, Roberto Turolla et al. (+9 more)
We report on the detection of polarized X-ray emission from the new Galactic magnetar EP J223759.5+531421, discovered by the Einstein Probe Wide-field X-ray
Telescope on 2026 June 28. The Imaging X-ray Polarimetry Explorer (IXPE) follow-up observation started on 2026 July 6 and detected the source at a (absorbed) flux of $\approx 4.5\times 10^{-11} \, \mathrm{ erg\,cm^2\,s}^{-1}$ ($2$–$7.5\, \mathrm{keV}$ range), confirming the presence of two thermally emitting regions on the
star surface, with temperatures $\approx 0.5$ and $\approx 1\, \mathrm{keV}$. A significant (at $> 4\sigma$ confidence level) phase- and energy-integrated polarization degree of $\approx 7\%$ was detected with the polarization angle $\approx -2^\circ$ East of the celestial North. The two thermal components exhibit quite different polarization properties, with the hotter one being more polarized. The difference is larger in the phase-folded data, with the polarization degree reaching $\sim 63\%$ in the range $4$–$7.5\,\mathrm{keV}$, in correspondence with the secondary peak of the pulse profile, and never exceeding $\sim 30\%$ at lower energies. The polarization angle continuously oscillates from $-90^\circ$ to $+90^\circ$ over one rotational cycle and is well fit by the rotating vector model, with an inclination of the line of sight and of the
magnetic dipole axis relative to the
star spin axis of $\approx 28^\circ$ and $\approx 109^\circ$, respectively. The data point to an emission geometry in which the cold thermal component likely originates from two antipodal caps, possibly in a magnetically condensed state, while the hotter one comes from a smaller region covered by an atmosphere.
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All authors Roberto Taverna, Lorenzo Marra, Roberto Turolla, Ruth M. E. Kelly, Silvia Zane, Alice Borghese, Francesco Coti Zelati, Paolo Esposito, Gian Luca Israel, Nanda Rea, Haonan Yang, Yilong Wang
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Big Bang Nucleosynthesis Confronts Domain Walls and First-Order Phase Transitions as the Pulsar Timing Array Explanations
Fatemeh Elahi, Diego Fortini, Yann Gouttenoire et al. (+2 more)
Pulsar timing arrays (PTAs) have detected a nanohertz gravitational-wave background, often attributed to annihilating domain walls (DWs) or first-order phase transitions (FOPTs). Their reheating imprints fluctuations in the baryon-to-
photon ratio. These so-called baryon isocurvature fluctuations $S_B$ survive until Big Bang Nucleosynthesis, whose yields depend nonlinearly on it. Modest $S_B$ fluctuations can therefore alleviate the current deuterium tension in parts of the PTA preferred regions and therefore strengthen their interpretation. Overabundant DWs and too strong FOPTs overproduce $D/H$ and are ruled out.
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All authors Fatemeh Elahi, Diego Fortini, Yann Gouttenoire, Nicholas Leister, Pedro Schwaller
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Gravitational Imprints of Dark Energy in Neutron Stars
O. P. Jyothilakshmi, Lakshmi J. Naik and V. Sreekanth
We investigate, for the first time, the non-radial $f$-mode oscillations of
neutron stars (NSs) with a dark energy (DE) core utilising a fully general relativistic treatment. We construct the stellar profile by considering a relativistic mean field model for nuclear matter and a modified Chaplygin fluid like prescription for DE. We compute the stellar structure, $f$-mode oscillations, tidal deformability, and gravitational wave (GW) energy and strain of the NS with DE core by varying the DE equation of state (EoS) parameters. Our study reveals that the inclusion of DE softens EoS and reduces the maximum mass compared to the pure
neutron star. The obtained mass-radius values are consistent with observational constraints from massive
pulsars such as PSR J0030+0451 and PSR J0740+6620. We find that the extent of the DE core, determined by the transition density, plays a crucial role in modifying the stellar structure and oscillation properties, with lower transition densities producing appreciable changes over a wider mass range. The $f$-mode frequencies and damping times exhibit systematic modifications, for higher mass configurations, while the correlation between the $f$-mode frequency and tidal deformability remains consistent with observational constraints from GW170817 and GW190814. Further, the normalised oscillation energy distribution remains nearly universal, with only minimal deviations for the higher mass configurations. Finally, we estimate the characteristic GW strain associated with the $f$-mode oscillations and find that the predicted signals lie within the sensitivity band of future third generation GW detectors.
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Solar and Stellar Astrophysics
CME Kinematics with Optical Flow: Multi-Coronagraph Insights into Internal Velocity Dispersion
Pritam Das, Vaibhav Pant and Neeraj Rathore
Coronal mass ejections (CMEs) exhibit poorly understood internal velocity distributions. In this work, we introduce an optical flow-based method, DOFCAT (Dense Optical Flow CME Analysis Tool), applied to high-resolution data from ASPIICS/Proba-3 and METIS/Solar Orbiter to examine the internal velocity dispersion of different substructures within CMEs in the Middle Corona. We also introduce a Gaussian-tapered
Fourier (GTF) filter that suppresses brightness artifacts in running-difference images from the ASPIICS wideband channel. We then apply DOFCAT to four CME events observed across ASPIICS and METIS, extracting their internal velocity information. Our results show that the velocity profiles of both the CME front and core change with position angle and are non-uniform. For impulsive CMEs, the height offset between the front and core begins to increase following the impulsive acceleration phase, while CMEs without a clear impulsive phase show a more gradual
evolution of the height offset. We find that this increase in height difference occurs rapidly between 2.3–3.0\,R$_\odot$. Furthermore, the front shows a higher velocity spread than the core, with impulsiveness evident in the CME leading half. We further compute the radial self-similarity coefficient separately for the front and the core, finding that the front expands non-self-similarly initially and tends toward self-similarity at larger heights, while the core remains relatively self-similar. These findings confirm that CMEs contain complex internal flows and layered substructures within the traditional three-part morphology. Our results demonstrate the utility of DOFCAT on high-resolution coronagraphs for probing CME dynamics and provide new insights into CME initiation and
evolution.
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Astrophysics of Galaxies
Rest-Frame UV and Optical Structural Evolution of Narrowband-Selected Lyman-alpha Emitters at z = 2-7 with JWST/NIRCam
Ronaldo Laishram, Haruka Kusakabe, Satoshi Kikuta et al. (+8 more)
We present a systematic study of the rest-frame ultraviolet (UV) and optical morphologies of Ly$\alpha$ emitters (LAEs) at $z \simeq 2$-$7$ from the SILVERRUSH multi-narrowband catalog, using JWST/NIRCam imaging from COSMOS-Web. We fit Sérsic profiles in four NIRCam filters (F115W, F150W, F277W, F444W) for LAEs spanning $\sim 2.2$ Gyr of
cosmic time. LAE sizes show a mild increase from rest-frame UV to optical wavelengths, with a median optical-to-UV size ratio of $R_{e,\rm opt}/R_{e,\rm UV} = 1.14^{+0.01}_{-0.02}$, indicating a small morphological $K$-correction; this offset is significant at $z \leq 5.7$ but not at $z = 6.6$. The rest-frame optical sizes follow a power-law
evolution, given by $R_e \propto (1+z)^{-0.94 \pm 0.09}$, decreasing from $0.91^{+0.07}_{-0.07}$ kpc at $z = 2.2$ to $\sim 0.5$ kpc at $z \gtrsim 5$, in close agreement with a recent JWST study of spectroscopically confirmed LAEs. The rest-frame optical size-mass relation slopes are broadly consistent with those of the general
star-forming
galaxy (SFG) population, while LAEs lie below it in normalization over $z \sim 3$-$6$. More compact LAEs tend to exhibit higher Ly$\alpha$ equivalent widths, a trend driven mainly by the most compact, marginally resolved sources. These compact systems also occupy elevated SFR surface-density regimes, consistent with a scenario in which concentrated
star formation may facilitate Ly$\alpha$ escape. No significant correlation of LAE rest-frame optical size with projected large-scale environment is found over $z \simeq 2$-$7$, suggesting that LAE morphology may be governed primarily by internal
galaxy properties, except possibly in the most extreme overdensities.
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All authors Ronaldo Laishram, Haruka Kusakabe, Satoshi Kikuta, Shunta Shimizu, Yusei Koyama, Tadayuki Kodama, Michaela Hirschmann, Greta Toni, Carter Flayhart, Rasha M. Samir, Novan Saputra Haryana
High Energy Astrophysical Phenomena
Kink instability as a particle acceleration mechanism in X-ray binaries and the connection to the outburst cycle
Emma L. Elley, James H. Matthews, Alex J. Cooper et al. (+2 more)
We consider whether the kink instability can explain particle acceleration in hard state 'compact' X-ray binary jets. We apply a 1D model to assess the expected growth rate of the instability for a variety of jet models, then scale results from simulations to estimate a dissipation rate for the
magnetic energy in the jet. We then consider the effects of radiative cooling on the system. We find that hard state 'compact' X-ray binary jets are likely to be unstable to the kink instability within their acceleration zones across a plausible parameter space. We further find that depending on the parameters of the model, the jets may radiate over a variety of length scales ranging from length scales attributable to a 'failed' jet scenario, to those in keeping with resolved
radio observations of 'compact' jets. We discuss the expected
evolution of this model through the outburst cycle.
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All authors Emma L. Elley, James H. Matthews, Alex J. Cooper, Fraser J. Cowie, Rob Fender
High Energy Astrophysical Phenomena
A Brief Review on the Statistical Properties of Fast Radio Bursts
Yu Sang and Hai-Nan Lin
Fast
radio bursts (FRBs) are millisecond-duration
radio transients of extragalactic origin, whose emission mechanisms and progenitors remain unresolved. Statistical analyses of the rapidly growing samples provide a promising means to constrain the underlying physics. In this review, we synthesize the statistical properties derived from current FRB catalogs, encompassing constraints on dispersion measure,
redshift, energy/luminosity functions, repetition rate, and host-
galaxy demographics. For repeating FRBs, we examine the statistics of energy, fluence/flux, waiting time, and discuss time-series analyses that reveal
memory effects and chaotic dynamics. We further discuss the observational discovery and theoretical interpretation of periodic activity, and survey polarization properties that probe the magneto-ionic environments of FRB sources. Throughout, we emphasize robust empirical trends, account for observational biases and selection effects, and outline outstanding open questions regarding the physical origin of these enigmatic bursts.
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Earth and Planetary Astrophysics
Molecular mapping of an exoplanet with JWST: NH3 detection in the temperate super-Jupiter Epsilon Indi Ab
R. Kravtchenko, O. Berné, I. Schroetter et al. (+2 more)
Epsilon Indi Ab is currently the coldest, and one of the closest, directly imaged
exoplanets (T_eff = 275 K, d=3.6 pc), offering a unique opportunity to test our understanding of the physical and chemical properties of gas giants across the full temperature range spanned by hotter directly imaged
exoplanets and the cooler giants of the Solar System. We aim to characterize the atmosphere of Epsilon Indi Ab using infrared spectroscopic observations. We present JWST spectroscopic observations of Epsilon Indi Ab obtained with MIRI in the Medium Resolution Spectrograph mode (4.9-27.9 microns, October 2025) and NIRSpec in the Integral Field Unit mode (2.87-5.27 microns, May 2026). The data are highly contaminated by the stellar light from the bright host
star. We therefore adopt a high-pass filtering and cross-correlation approach based on petitRADTRANS atmospheric models to detect the planetary signal and specific molecules. The cross-correlation analysis enables a robust detection of the
planet with both instruments (up to S/N = 15.2). Using molecular mapping, we securely identify the presence of NH3 (maximum S/N = 15.6), H2O (maximum S/N = 10.8), CH4 (S/N = 3.8) and marginally detect CO2 (S/N = 2.5). These first results confirm the potential of infrared spectroscopy combined to cross-correlation techniques to characterize the atmosphere of directly imaged
exoplanets with JWST, even the in case where the contamination by the host
star is critical.
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All authors R. Kravtchenko, O. Berné, I. Schroetter, P. Amiot, F. Debras
Astrophysics of Galaxies
Mass Distribution of M31 from its Rotation Curve up to 167 kpc
Hao Wu, Yang Huang, Huawei Zhang et al. (+2 more)
The mass distribution of the Andromeda
galaxy (M31) is fundamental for understanding its dark matter content, assembly history, and dynamical role within the Local Group. However, estimates of M31's total mass remain quite uncertain, partly because of limited dynamical constraints at large galactocentric radii. Moreover, M31's recent merger history has produced abundant tidal substructures and may have left its outer
halo out of dynamical
equilibrium, complicating
equilibrium-based mass estimates. We use over 8,500 tracers with line-of-sight velocities to constrain the rotation curve (RC) of M31 over R=2–167 kpc. In the disk, we derive the RC from a clean tracer sample using the Jeans equation and find good agreement with previous H I measurements. In the
halo, we use Gaussian mixture modeling to account for tidal substructures and Galactic foreground contamination and constrain the kinematics of the residual dynamically hot
halo. Assuming this
halo population can be treated as an
equilibrium tracer, we infer the outer RC and constrain M31's mass distribution for different velocity anisotropies beta and dark matter
halo profiles. The NFW and Dekel–Zhao (DZ) models yield broadly consistent total masses ranging from 1.12(+0.11/-0.10) to 1.63(+0.21/-0.17)x10^12 Msun for beta=0.3–0.7. In contrast, the Einasto profile favors substantially lower masses of 0.41(+0.09/-0.06) to 0.86(+0.21/-0.16)x10^12 Msun, highlighting significant dependence on the adopted
halo profile, although Einasto solutions are more in tension with independent mass estimates based on M31 satellite
galaxies than the NFW and DZ models at fixed beta. Overall, our analysis provides a comprehensive measurement of M31's mass distribution under the assumption of dynamical
equilibrium, while also quantifying the systematic uncertainties associated with
halo velocity anisotropy and the choice of dark matter density profile.
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All authors Hao Wu, Yang Huang, Huawei Zhang, Qikang Feng, Cheng Liu
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Dark Diffraction at LZ from a Screened Neutral Composite Baryon
Hyunjoo Jung and Seong Chan Park
The LUX-ZEPLIN (LZ) experiment recently reported a nuclear-recoil-like candidate at $E_R=248\pm23_{\rm stat}\pm23_{\rm sys}$ keV. We show that such an energetic recoil can arise from the elastic form factor of composite dark matter, without invoking an inelastic mass splitting or a boosted population. A neutral baryon of $N$ dark
quarks can have a charge form factor that is suppressed at low momentum transfer but recovers at higher momentum transfer, providing a momentum-space band-pass filter. Modeling the form factor with one Gaussian per charged constituent species, we prove that two terms cannot produce a hard recoil spectrum and find that three yield too few events in the LZ signal window, while four suffice. A confining $SU(4)_D\times U(1)_D$ gauge theory provides a concrete realization through a neutral bosonic baryon made of four dark
quarks. For a 200 GeV
benchmark normalized to one accepted event, we predict approximately 1.5 true recoils beyond the current LZ region of interest. The form factor also produces diffraction nodes at fixed momentum transfers, placing them at recoil energies that scale as $1/m_A$ across target
nuclei.
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High Energy Astrophysical Phenomena
A Multi-Mission Detection Framework for High-Energy Transients: Application to a 13-year Fermi/GBM and Swift/BAT Sample
Ariel Perera, Barak Zackay and Tejaswi Venumadhav
The detection of faint high-energy transients is becoming increasingly important in time-domain and multi-messenger astronomy, particularly for identifying electromagnetic counterparts to binary
neutron star mergers, high-energy
neutrino events, and other weak transient phenomena. At present, the sensitivity of gamma-ray and hard X-ray searches is often limited by the detection threshold of individual instruments, leaving a population of faint transients inaccessible to single-mission analyses. To address this limitation, we develop a joint detection framework that combines trigger information from multiple detectors and assigns each candidate a joint association probability, $p_{\text{joint}}$, as a function of the individual detector signal-to-noise ratios. We apply this framework to archival Fermi/GBM and Swift/BAT rates data from 2013-2025. The method effectively separates coincident signals from accidental background associations, suppressing inconsistent coincidences while enhancing the significance of faint events observed by both instruments. We find that, under optimal conditions, a two-mission search can increase the accessible volume for short gamma-ray bursts by up to $60\%$. This framework provides a practical foundation for generalized multi-mission searches, enabling more sensitive exploration of the faint high-energy transient sky and improving the prospects for future multi-messenger discoveries.
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Cosmology and Nongalactic Astrophysics
Probing the Mass–Redshift Dependence of Binary Black Holes and its Implications for $H_0$ with GWTC-5.0
Yang Liu, Puxun Wu, Jun-Jie Wei et al. (+1 more)
The mass and
redshift distributions of merging binary black holes (BBHs) bear imprints of their astrophysical formation channels. Whether the BH mass distribution evolves with
redshift, however, remains an open question. In this paper, we employ copula functions, which describe the dependence between variables independently of their marginal distributions, to probe the dependence structure between the primary mass and the
redshift of BBH mergers. We construct five population models by coupling the marginal distributions of primary mass and
redshift with the Gaussian copula, the Clayton copula, or one of its three rotations, and we constrain their hyperparameters using 235 BBH events from GWTC-5.0. For comparison, we also adopt a baseline model in which the primary mass and
redshift are assumed independent. Among the copula-based models, only the model with the $180^\circ$ rotated Clayton copula, which couples higher primary masses preferentially with high
redshifts, exhibits evidence for a nonzero correlation, with its copula parameter deviating from the independence limit at more than $1\sigma$ significance. Importantly, the constraints on the Hubble constant ($H_0$) derived from these models are mutually consistent within the $68\%$ confidence level; the baseline model yields $H_0=74.3^{+13.7}_{-19.6}~\mathrm{km\ s^{-1}\ Mpc^{-1}}$, indicating that allowing for a mass–
redshift dependence does not significantly bias the $H_0$ inference with the current
dataset.
Bayesian model comparison favors the baseline model over all copula-based alternatives, with log-Bayes factors corresponding to weak to moderate evidence against the latter on the Jeffreys scale. Our results thus imply that the current GWTC-5.0 sample remains consistent with no
redshift evolution of the primary mass distribution over the
redshift range probed.
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All authors Yang Liu, Puxun Wu, Jun-Jie Wei, Xue-Feng Wu
Instrumentation and Methods for Astrophysics
Fitting Moving Objects in Up-The-Ramp Data with Applications to the Roman Space Telescope and JWST
Timothy D. Brandt
A moving object breaks the fundamental property of constant per-pixel count rates in an astronomical image read out up-the-ramp. In this paper, we show how to fit a moving object's path across a detector as that detector is read out nondestructively. We write the full likelihood function for every pixel subject to a constant count rate plus a time-dependent count rate due to a moving source. Assuming the moving source to be point-like and assuming the effective point-spread function to be known, we are left with four parameters that enter the likelihood nonlinearly: two for position and two for velocity. All remaining parameters can be optimized using closed-form expressions. Our approach extracts maximal information on a moving source's position and speed and enables the source to be accurately removed from the image. We investigate the dependence of flux, position, and velocity precision on the target's speed and the readout pattern. We also find a small, positive bias on the recovered flux due to the need to fit for an uncertain position and speed. Our approach can be used for space-based images with minor Solar system bodies in the foreground, e.g.~from Roman and JWST, or for ground-based observations with satellites in the foreground. We demonstrate the promise of our method with a fit to an asteroid track observed serendipitously by the NIRISS instrument on JWST, comparing it to the performance of the JWST pipeline. Python code implementing our approach is available at https://github.com/t-brandt/moving_source. The total computational cost to fit the track of a moving object is $\sim$1 second on a 2023 Macbook Pro.
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Cosmology and Nongalactic Astrophysics
HierArchical Wavelet Coefficients on the Sphere (HAWCS): the Scattering Transform on Spherical Maps
Arefe Abghari, Lukas T. Hergt, Douglas Scott et al. (+1 more)
Extracting Gaussian information from data is well understood, but characterizing non-Gaussianity is challenging. We introduce HAWCS, a healpy-based Python package for efficiently computing wavelet scattering transform coefficients from full-sky maps. These coefficients provide compact summary statistics that are sensitive to higher-order structure and interactions across angular scales. We test the implementation on controlled Gaussian and non-Gaussian fields and demonstrate its computational efficiency. We then apply HAWCS to thermal Sunyaev-Zeldovich maps derived from Planck observations and four simulations, quantifying and comparing their higher-order statistical properties. We also use the method to expose the signatures of gravitational
lensing in
cosmic microwave background (CMB) temperature maps. These results demonstrate that HAWCS is a practical tool for validating component-separation pipelines and cosmological simulations, and a promising summary statistic for characterizing non-Gaussian structures beyond the power spectrum. These coefficients could also be used to constrain or generate simulated maps that reproduce the same statistical features of real data.
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All authors Arefe Abghari, Lukas T. Hergt, Douglas Scott, Raelyn M. Sullivan
Earth and Planetary Astrophysics · Cross-listed from math.DS
Identifiable Uniqueness of Impulsively Forced, Inert, and Stabilized Body Trajectories
Bo Pieter Johannes Andrée
An unusual object in the sky raises two related questions: what kind of object it is and what physical process drives its motion. Departures from a
gravity-only trajectory can provide evidence, but the same apparent acceleration may be generated by distinct dynamical mechanisms. We formulate this as an identification problem and establish conditions for identifiable uniqueness among three reference classes: inert dynamics, impulsive forcing, and active stabilization such as a controlled spacecraft. The distinction rests on how each class responds to disturbances. Although different mechanisms can produce similar average trajectories, the specified reference models imply different
stochastic responses around those trajectories. We show when these differences uniquely determine the dynamical class from the observed trajectory and when several classes remain observationally compatible.
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Earth and Planetary Astrophysics
Possible Observational Survey Strategies to Maximize Exoplanet Yields: A Report from the Survey Strategies Task Group in the Exoplanet Science Yields Working Group
Natasha Latouf, Corey Spohn, Kevin Fogarty et al. (+12 more)
We present a variety of possible observational sequences from
planet detection to characterization (i.e., survey strategies) for the initial exoEarth detection and characterization survey phase of the Habitable Worlds Observatory. An array of survey strategies were collated by the HWO
Exoplanet Survey Strategies Task Group; by investigating and comparing expected resultant exoEarth yields for multiple survey strategies, we can better understand the most efficient strategy to characterize multiple
planets in unconventional ways. We present eight varied survey strategies, presented as steps of Detection, Photometry, Orbit Measurement, and/or Characterization, including discussion of possible shortcomings and benefits of each strategy. We present exoEarth yield calculations from the Altruistic Yield Optimizer (AYO) and the
Exoplanet Open-Source Imaging Mission Simulator (EXOSIMS) for select strategies, with initial considerations of thermal emission and detector noise. Herein, a yield is the expectation value given the astrophysical assumptions of the number of
planets that meet the observational criteria during the survey. We find that AYO and EXOSIMS find the highest yields for H2O at 0.9 microns, although the calculated yields vary. When allowing for wavelength optimization within AYO, we find that H2O is most optimal to observe at 0.9 microns when given the full range of VIS and NIR values, with an expected exoEarth yield of 29.1. H2O and O2 dual characterization is possible at the expense of yield
planet loss, with a calculated possible yield of 20.9 in the VIS. The characterization of CH4 and CO2 in the NIR result in the lowest exoEarth yields at 19.9 and 6.4 possible expected
planets, respectively. Future work updating AYO and EXOSIMS is necessary to explore further survey strategies that follow different observation procedures, some of which is currently underway.
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All authors Natasha Latouf, Corey Spohn, Kevin Fogarty, Chris Stark, Dmitry Savransky n=and Eleonora Alei, Anthony Boccaletti, Gagandeep Kaur, Avi Mandell, Rhonda Morgan, Aki Roberge, Jean-Baptiste Ruffio, Jean Schneider, Edward Schwieterman, Armen Tokadijan, Daniel Viudez-Moreiras
Solar and Stellar Astrophysics
Evidence for the emergence of stellar magnetic fields during rapid mass transfer
Gregg A. Wade, Tomer Shenar, Pablo Marchant et al. (+6 more)
Binary interaction fundamentally alters the
evolution of massive
stars, yet the physical consequences of mass transfer remain poorly constrained. Here we present high-resolution spectroscopic observations of Plaskett's
Star (HD 47129) that reveal small radial-velocity variations of its
magnetic secondary, coherent with the system's 14.4 d orbital period. These measurements support an evolved, post-mass-transfer configuration in which the narrow-lined primary is a partially Roche-lobe-filling stripped
star with a mass of $5.9^{+1.8}_{-1.4},M_\odot$, while the secondary is a $40.8^{+9.3}_{-6.7},M_\odot$, rapidly rotating
magnetic accretor. The system provides a rare opportunity to observe the immediate aftermath of mass transfer in a massive binary and offers compelling new evidence linking binary interaction to the emergence of strong stellar magnetism. Because
magnetic fields regulate angular-momentum loss and transport, their formation through mass transfer could alter the subsequent
evolution of massive binaries, with consequences for stellar populations,
supernova progenitors and yields, and the formation of gravitational-wave sources.
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All authors Gregg A. Wade, Tomer Shenar, Pablo Marchant, Michael Abdul-Masih, Matteo Cantiello, Jason Grunhut, Oleg Kochukhov, Hugues Sana, Selma E. de Mink
Earth and Planetary Astrophysics
Large-scale chaos in restricted hierarchical triples driven by short-range forces
Xiaoyan Leng and Hanlun Lei
Context: The eccentric von Zeipel-Lidov-Kozai effect, which is widely applied to diverse astrophysical settings, can drive the inner binary to extremely high eccentricities, where short-range forces such as general relativity (GR) become prominent. Aims: Poincare surfaces of section show that GR effects reshape phase-space structures, giving rise to a widespread and large-scale chaotic sea. This work aims to uncover the underlying mechanism of GR-enabled chaos. Methods: The dynamical structures are studied within an adiabatic framework, where an adiabatic invariant is constructed. Phase portraits, defined by the level curves of this invariant, establish analytical boundaries for the chaotic domains. Numerical simulations are subsequently performed to map orbital flips, maximum eccentricities, and Fast Lyapunov Indicators (FLI) across the initial eccentricity-inclination parameter space. Results: Phase portrait analysis demonstrates that GR precession introduces an uncertainty zone near polar inclinations, where trajectories crossing this zone inherently become chaotic. Leveraging this framework, the chaotic boundaries across the full parameter space are analytically derived, yielding excellent agreement with numerical maps of flipping orbits, maximum eccentricity, and FLI. Conclusions: In the presence of short-range forces, flipping orbits accompanied by extreme eccentricity excitation are fundamentally chaotic, and the underlying mechanism of large-scale chaos originates from the periodic passage of trajectories through the uncertainty zone in phase space over secular timescales.
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